1. Field of the Invention
The present invention relates to a television receiver which is suitable for a picture tube having an aspect ratio (a ratio of horizontal side to vertical side of the display screen of a picture tube), for example, of 16:9.
2. Description of Related Art
In the current standard television system (for example, the NTSC system, etc.), the aspect ratio is determined, as is well known, to 4:3 (ratio value is 1.33). Moreover, in the newly proposed high-definition television (Hi-Vision) system, since the aspect ratio is determined to 16:9 (ratio value is 1.78), the lateral side of the display screen is wider than that in the NTSC system.
In these years, software for such a wide display screen is increasingly put into application. In this case, materials of movie programs for a wide display screen of the so-called vista size (aspect ratio value is 1.85) and CinemaScope size (aspect ratio value is 2.35) are accommodated in the screen in the letter box type with the aspect ratio of 4:3 without any trimming. Moreover, television broadcast programs for wide display screen are also increasing in numbers as well as the programs where the Hi-Vision broadcast signal is down-converted to the NTSC signal.
In compliance with the increase of such software and broadcast programs for the wide display screen, a wide display screen television receiver, which employs a picture tube with the aspect ratio of 16:9 and 525 scanning lines corresponding to the NTSC system and which is also called a laterally wide television receiver or just a wide television receiver, has been made available in the market.
On the occasion of displaying the software of movie programs for wide display screen on the television receiver of the NTSC system, the blanking period wherein any video or picture information is not included is often inserted at the upper and the lower portions of the display screen. For example, when a program is displayed on the receiver utilizing a picture tube having the aspect ratio of 4:3, a wide picture Pw is displayed fully in the horizontal direction on the display screen of the picture tube (hereinafter called the standard display screen. A picture having the aspect ratio of 4:3 is called the standard picture.) SCn as shown in FIG. 5A and the blanking region is formed at the upper and lower portions of the standard display screen SCn corresponding to the blanking period not including any picture information as indicated by the hatched areas in FIG. 5A.
Moreover, when software for the wide display screen is displayed on a wide display screen television receiver, the blanking regions are also formed at the upper and lower portions of the wide display screen SCw of the television receiver. Therefore, in the wide television receiver, for example, as described in the Laid-Open Publication No. Hei 2-305190 laid opened on Dec. 18, 1990, it is detected that the relevant software is a wide picture program of the vista size and CinemaScope size or not, depending on the length of the blanking period not including any picture information. When the program is detected as software for the wide display screen, the vertical amplitude is expanded for display on the wide display screen SCw.
For instance, in the case of a material of vista size program, as shown in FIG. 5B, a widely expanded picture Pzv is displayed almost in the full size of wide display screen SCw of the television receiver by expanding the vertical amplitude with a rate of the aspect ratio of the wide display screen SCw having the aspect ratio of 16:9 and the vista size display screen.
In the present specification, a mode where a wide picture Pzv expanded in the vertical direction is displayed in full size of the wide display screen SCw as shown in FIG. 5B is called the zoom mode.
In the case of this zoom mode, the blanking regions formed at the upper and lower portions of the display screen are located outside the wide display screen SCw and only the desired picture is expanded and displayed in full size of the display screen to enhance the feeling of being at the live performance at the time of watching the television program.
Moreover, in the case of letter box type software, the positions of pictures accommodated are different depending on the software and when software offers a foreign movie, a superimposed dialogue translated into Japanese is usually inserted at the lower part of the display screen. Therefore, the center of expansion in the vertical direction cannot be fixed. Accordingly, in the case of the zoom mode in the wide display screen television receiver, the display screen can be scrolled in the vertical direction up to the condition where only the upper end or lower end portions of the expanded picture Pzv is lost by changing the phases of the vertical synchronous signal and video signal.
Meanwhile, in the case of the wide display screen television receiver, when the standard picture Pn having the aspect ratio of 4:3 is displayed in the full size of the wide display screen SCw in the vertical direction with such aspect ratio kept unchanged, the blanking regions are formed at both right and left end portions of the display screen SCw as shown in FIG. 6A.
In the present specification, the mode where the standard picture as shown in FIG. 6A is displayed fully on the wide display screen SCw in the vertical direction with the aspect ratio of 4:3 kept unchanged is called the normal mode.
In this normal mode, the wide display screen is not used in its full size, but even if the standard picture is simply expanded in the horizontal direction as shown in FIG. 6B, the geometrical fidelity of the picture is deteriorated, providing an elongated picture Pnh.
Therefore, a wide mode technology has been developed. In this mode, the standard picture can be naturally displayed on the wide display screen without any sense of incongruity by expanding both right and left end sides in the horizontal direction while the center of the display region is kept unexpanded to eliminate the blanking regions in the right and left sides in the normal mode in view of enjoying the standard picture with the wide display screen.
In the case of this wide mode, the picture is a little expanded in the vertical direction and the vertical linearity is compressed at both upper and lower end portions of the display screen.
Cited reference: "Wide Television" by Ohnishi Proceedings of Japanese Society of Television, No. 7, Vol. 47 (July, 1993)